Capability of SCRT® Configuration to Achieve Ultra Low NOx Standards

Liu  Yang, Johnson Matthey

As engines evolve to improve fuel efficiency to achieve tighter greenhouse gas standards, the exhaust profile of these engines is undergoing significant change. The impact of these changes on commercially available aftertreatment systems are required to establish a baseline for catalyst and aftertreatment system development. Here, the system performance of an SCRT® after-treatment system was simulated over cold-start and hot-start FTP and low load cycles from a modified engine calibrated by Southwest Research Institute (SwRI) to understand the lowest possible emissions that could be achieved for future engines. The SCRT® after-treatment system is composed of a Diesel Oxidation Catalyst (DOC), Catalyzed Diesel Particulate Filter (cDPF), Selective Catalytic Reduction (SCR) Catalyst, and NH3 slip Catalyst (ASC). Catalytic models of the best commercially available technologies were incorporated at today’s average SCR volume to understand the barriers to achieving ultra low NOx standards. We will show how, with catalyst optimization, a NOx emission of 0.021 g/bhp-hr was simulated over the FTP. Additionally, we will describe the impact of parameters such as pre-NH3 storage and heated dosing have on the simulated system’s ability to achieve 0.18 g/bhp-hr over a Low Load Cycle (LLC). For the LLC, we will also describe the calculation of Moving Average Windows (MAW), the impact of purposed power thresholds on the final emissions and the sensitivity of the system to pre-NH3 storage and heated dosing.